Treatment of pyrrhotite ores



TREATMENT PYRRHOTITE ORES Worth Martin'Fitzsimmons, Stamford, Conn., assignor to American Cyanamid Company, New York, N. Y., a corporation of Maine No Drawing. Application December 5, 1951, Serial No. 260,096

8 Claims. (Cl. 209-166) This invention relates to the treatment of refractory pyrrhotite ores by froth flotation. More particularly, the invention relates to the treatment of pyrrhotite ores containing nickel and platinum values in additon to chromium oxide minerals.

In certain ores a refractory type of pyrrhotite occurs which cannot be readily floated with the ordinary sulfide collectors. The problem is particularly acute in certain nickeliferous pyrrhotite ores containing platinum associat ed with the pyrrhotite and which also have a large content of chromium oxide in the form of chromite. Such an ore deposit, for example, is found in the Philippine Islands.

According to the present invention, it has been found that'if the ore is treated with an inorganic fluorine compound such as hydrofluoric acid, sodium fluosilicate and the like, the surface of the refractory pyrrhotite is altered and the pyrrhotite is then readily floated with conventional sulfide collectors such as xanthates, dithiophosphates and the like and a good separation is made from the gangue and chromite which is'also present in the ore. Itshould be understood that the action of the fluorine compound affects the flotability'of the pyrrhotite. This action has nothing in'common, and should not be confused with the action of fluorine compounds in improving the flotation of various oxidized minerals. In fact, the action is actually substantially the reverse as the effect of the fluorine is notto enhance the flotation of the oxide minerals but, on the contrary, to activate the slow-floating sulfide, pyrrhotite. The exact mechanism is not fully known, but it is thought that one factor may be the presence of thin silicate coatings on pyrrhotite particles with which the fluorine compounds may react. Other factors may, however, play a part and it is therefore not desired to limit the invention to this particular theory of action of the fluorine compounds.

Application of the inorganic fluorine compound to the ore involves contact under acid conditions. Thus the ore may be conditioned with hydrofluoric acid and flotation then effected, a non-acid inorganic fluorine compound such as sodium fiuosilicate may be used with sufli-' cient acid, or the actual contact with the ore may be effected in the flotation circuit itself. Thus, for example, the ore can be conditioned with sodium fluosilicate and sulfuric acid added to the flotation cell or, alternately, the flotation may be eifected with hydrofluoric acid. While it is not necessary that the fluorine compound and acid' be both introduced in the conditioning step, best results \are obtained under such circumstances, and this'constitutes the preferred embodiment of the present invention. I The exact order of treatment is not rigidly limited but {l prefer to condition first with sufiicient acid to assure the requisite acidity in flotation; then condition the ore I to the-sulfide flotation by which the pyrrhotite and its associated metal values are recovered.

gAIthOugh'the present invention is not-limited to the 2,093,278 Patented Nov. 2, 1954 use of any particular sulfide collector, I have found that there is a considerable variation in the efliciency of different collectors, the best results being obtained with amyl xanthates. In a more specific aspect, therefore, the use of this collector is included. The invention will be described in greater detail in conjunction with the following examples. The metallurgical results for the examples are given in a table at the end.

Example 1 A chromite ore containing a nickeliferous pyrrhotite with'associated platinum values obtained from a Philippine deposit was ground with 5 lbs. per ton of sodium carbonate, and deslimed at 22% solids with 7 lbs. per ton of crude lignin sulfonate as a dispersant. 'The ore was then stage floated at a pH of 6.8 with 0.7 lb. per ton of potassium amyl xanthate, 10 lbs. per ton of sulfuric acid, 2 lbs. per ton of copper sulfate and 0.3 lb. per ton of a higher paraflin alcohol until no more sulfides were recovered. Total time of float was 60 minutes. The rougher concentrate was then conditioned for a short time with an additional 10 lbs. per ton of sulfuric acid and floated to produce a cleaner concentrate. The rougher tailing was conditioned with 3 lbs. per ton of an oil-soluble petroleum sulfonate and a chromite concentrate floated off which was cleaned once. The addition of the potassium amyl xanthate, frother, and sulfuric acid, during the sulfide float was made gradually in stages.

This procedure represents what may be termed conventional practice in the flotation of pyrrhotite. A good grade of concentrate was obtained, but the recovery of platinum group metals and nickel was very poor. The ore used in this example contained approximately 0.4 ounce per ton of platinum group metals, 0.5% nickel and 30% CrzOs.

Example 2 The ore of Example 1 was ground and deslimed as described above and conditioned at low (18%) solids, first with 10 lbs. per ton of sulfuric acid and then with 6 lbs. per ton of hydrofluoric acid, and finally, with 0.1 lb. per ton of potassium amyl xanthate and 0.03 lb. per ton of the higher alcohol frother. A sulfide float was effected in a much shorter time than in Example 1, approximately one-ninth as long. During the float there were added in two portions, at intervals, an additional 6 lbs. of hydrofluoric acid, 0.15 lb. per ton of the xanthate and 0.06 lb. per ton of the alcohol frother. The sulfide 0 concentrate without cleaning showed approximately the same grade of platinum group metals and nickel, and approximately double the recovery. The sulfide tail was then treated on a Wilfley table to recover the chromite.

The difference in time of float was chosen because in the first example the pyrrhotite floated so slowly that the maximum flotation was used in order to obtain the best possible recovery. Obviously, the flotation time in Example 1 is so long that it would constitute an unattractive operation from the standpoint of cost. The test was made to give optimum possible recoveries so that the comparison would be under the best conditions for each operation.

Example 3 The ore of Example 1 was ground, deslimed and conditioned first with 10 lbs. per ton of sulfuric acid then with 5 lbs. per ton of sulfuric acid and 2 lbs. per ton of sodium fluosilicate, and finally with 0.1 lb. per ton of potassium amyl xanthate. Froth flotation was then effected after adding 0.015 lb. per ton of the higher alcohol frother. The rougher float was eflected in a series of five stages, the same amount of sulfuric acid, sodium fluosilicate, xanthate, and frother being added at each step. The sulfide concentrate was then cleaned and the rougher tailing deslimed, conditioned with 0.5 lb. per ton of oleic acid and floated to produce a rougher chromite concentrate. The latter concentrate was cleaned with the addition of 0.015 lb. per ton of the frother. and 0.2 lb. per ton of oleic acid.

Example 4 The procedure of Example 3 was followed, but the meagre ore was ground more finely','the grinding time being 50% greater. Also; in the cleaning step, additional sulfuricacid, sodium fluosilicate, potassium amyl xanthate and frother were used in amounts'of 5.0, 2.0, 0.02 and 0.015 lbs. per ton, respectively;

Example .5

Example. 7

A Philippine: duniteore. containing nickeliferous pyrrhotite and associated platin m r up metals was ground andfloated in four. stages, eachfor -fiveminutes. In eachystage-the pHranged from-5i5"to-' 6.1. Inthe first stage there-were" 30"lbS.', of sulfuric :acidc'per ton," one pound per ton of secondarybutyl xanthate and 0.06 lb. per ton of dicresol-dithio-phosphoric-acid. Thesecond twostages were eifected eachwiththe addition'of 15 lbs; per ton'of sulfurieacid, 035 lb; per tonof secondary xanthate and 0.02 lb: per'ton'of' dicresol-dithio-phosphoric acid. In the :last stage the amountofsulfuric acid was lbsrper ton andOiS'lbnper 'ton-"of-potassium amyl xanthate was substituted for the secondary butyl xanthate. The ore analysed approximately 0.85 nickel with about 0.12 ounce per ton .ofplatinum group metals.

Example .8.

The -ore "of Example 7 Fwas conditioned first with 10 lbs. perton ofsulfuric acid, then with S'lbs. per 'ton of sulfuric acid and 2'-lbs.-p er ton-of-sodium fluosilicate, and finally with 0.10 lb. per ton of potassium amyl. xanthate. Flotation was effected for two minutes with'0i0'15 lb: per ton of a higher paraffin alcoholfrother. The conditioning with. sodium fluosilicate, xanthate, and frother, was .repeated in four more rougher. stages, except that. the amount of xanth'ate in each of "these stages .was reduced. to 0'.02:lb.' perton. The rougherqconcentratewas conditioned with- S.0lbs. pen'ton sulfuric acid, .2.0 lbs: per ton-sodium 'fluosilicate, 0.02 11h. per. ton :xanthate; and 01015 1b. perton higher .paraflin alcohol frother,-and'then floated for two-minutes for the production-pf a: cleaner in the flotation step 15 lbs. per ton of sulfuric acid were added and 5 lbs.- per ton of sulfuric acidineach of the following four flotation, steps, there being no conditioning outside of the flotation cell after each addition of acid. As in Example 9, the rougher concentrates were collected and assayed.

Example 11 The procedure of "Example 10' was followed except that 5 .lbs. per. .ton ,of sulfuric. .aoid .--Were added fro-the, pulp -.before conditioning 1 to. adjust: its pl-I to,7.,0. and the remaining 10 lbs. per ton of sulfuric .acid:;added-to the first flotation step. An additional 5 lbs. per ton of sulfuric acid were .aadded.in:..each' .of' .the. succeeding: flotation steps. As in Example:l0;anozconditioning was given after each float.

Example 12' The procedure. of. Example 11.wa s followedexcept that there was .no conditioning with-.sodium...fluosilicate,

nor was anyv sulfuric. acidadde'd .to ,the .flo'tationtcelll. Ina

stead, 2:6'1bjs. per ton. of 48%1hydrofluoric acid wasadde'd to the first step and'a similar amount. to..eachl.of Ithesucceeding four. stages... Therougher concentnateswere collected and .-,.assayed.,

The following tablein. which; the. recovery percentages are. rounded off. toith'e nearest. .whole. .numbe'r. shows v,thev

comparative. results of 7 Examples 9 to. .12, ,only 7 recovery of platinum group rmetalsdand-nickd being.;given.. For comparison purposes, the calculated;rougher.concentrate; ofExample 4 is given.

It ,willb'e noted'frorn the abovetable that.the .pr.esenceof'acidjisflessential. The use..of -an inorganic fluorine. compoundlalone .in. Example v9 does :not...giy:e .any-sig nificant. improvement over Example .1 ;in whichpno .commercially significant fluorine compound was present. Pracconcentrate, 50 t1ca1,..worthwh1le. improvements .weretqbtamed whemb m Assay Percent gsi gaggg Sulfide Chromite Concentrate Ex. Pt" OrzOa Group N1,. Pt': Ratio Metals, .Perf. Grou Nickel. .GmOe .ConcL of. oz. per cent Meta s j Grade, Ree.,. Cone.- ton= Percent Percent Rough'er flotation, noeleaning:

b 4.5-for'the first rougher-concentrate;2:5ior the next two and 2.4,ior the last, averaging 3.5,

Example 9 The ore of- Example l'was conditioned .with -2Ilb's. per

ton .of sodium fluosilicate and .then. with 0.1 1b.: per ton.

of potassium vamyl xanthate. Flotation. ,was then effected. with 0.015 lb. per. ton-of.ajhigher.alcoholjfrother. The. tailing was then conditionedjwith.an..additional 2" lbs... per ton of sodium.fluosilicate.=and='0i021lbl per ton of. potassium .amyl 'xanthate, .fljotationabeing; again. .elfe'ctedi with the same amount. ofihigheralcoh'olflfrother. This. second stepwas -then.rep eated-"fourtimes, Th'e.;tota1. rougher concentrate was coll'ectedandfassayed."

ExamplelO. The procedure .of Example 9. was .'fol1owed,...except that acid and fluorine: compound. were..pr.esent -.even .though. there was no conditioning .of .the :ore .with- .thea,two ..rna-.- terials prior to. flotation. Howeverg the resultsfall considerably short ..of thoseobtainablebyone ot-theme:- ferred procedures in Example 4 Where the fiuorine,com-.- pound and. acid .wereused :ll'li conditioning @theore before flotation took place.

Thisapplication is a continuation-in-part .ofyapplicae tion .5. N. 246,715, now abandoned.

I .claim':

1. As an .improved process :.of.floating.;a. refractory pyrrhot1te -.fr,om an me which contains .as itS- .Pl}lnCl.Pal..; values nickeliferous pyrrhotite containing platinumi'group, metals. associateddwith the. pyrrhotite, therimproved process which comprises subjecting the said ore under acid conditions to froth flotation in contact with a soluble inorganic fluorine-bearing ccanpound and a sulfide collector to produce arconcentrate relatively rich in nickeliferous pyrrhotite and platinum group metals and a tailing relatively poor in pyrrhotite.

2. The process of claim 1 in which the sulfide collector is a xanthate.

3. As an improved process of floating refractory pyrrhotite from an ore which contains as its principal values nickelifero'us pyrrhotite containing platinum group metals associated with the pyrrhotite, the improved process which comprises conditioning the said ore under acid conditions with a soluble inorganic fluorine-bearing compound and subjecting the so conditioned ore to froth flotation under acid conditions, in the presence of a sulfide collector to produce a concentrate relatively rich in nickeliferous pyrrhotite containing platinum group metals and a tailing relatively poor in pyrrhotite.

4. The process of claim 3 in which the sulfide collector comprises a Xanthate.

5. The process of claim 4 in which the sulfide collector comprises an alkaline metal amyl xanthate.

6. The process of claim 3 in which the inorganic fluorine compound' is hydrofluoric acid.

The process of claim in which the said ore con- References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,412,217 Havens Dec. 10, 1946 2,556,215 Queneau et al June 12, 1951 OTHER REFERENCES A. I. M. M. E. Technical Paper 1074, 1939, printed in Mining Technology, vol. 3, 1939 (16 pages). Copy in Division 55. 

